1. Field of the Invention
The present application is directed to manufacturing solar cell receivers, more particularly to precisely aligning and soldering solar cell receiver components on a metallized substrate.
2. Description of the Related Art
Direct Bonded Copper (DBC) substrates provide good heat and current transfer capability in addition to good electrical insulation, making DBC a suitable substrate choice for solar cell receiver applications. A typical DBC includes a ceramic member made of Alumina, AIN, BeO, etc. and a sheet of copper bonded to one or both sides of the ceramic member by a high-temperature oxidation process. The metallized surface of the DBC substrate is usually finished with nickel and immersion gold plating prior to any components being mounted on the substrate.
Components of a solar cell receiver such as a solar cell, bypass diode and electrical connectors are typically soldered to the metallized surface of the DBC substrate. For example, a solder paste can be screen printed onto certain portions of the DBC substrate which correspond to where the components are to be attached to the substrate. The components are then placed on the substrate. The DBC substrate is heated at an elevated temperature sufficient for the solder paste to reflow, attaching the components to the substrate.
The components often move around during solder reflow, causing the components to become misaligned from their initial desired placement. A solder mask or solder stop can be applied to the mounting surface of the DBC substrate for reducing component movement during the solder reflow process, but doing so significantly increases the cost of the solar cell receiver. In addition, it is undesirable to have a solder mask or other organic material on the mounting surface of the DBC substrate, since such materials can burn under high concentrations of stray sun beams which may arise if the solar cell receiver system does not perfectly track the sun.
Absent proper positioning control of the solar cell receiver components during assembly, the components become misaligned regardless of how accurate the components can be initially placed on a substrate. Movement during the solder reflow process typically results in a component positioning inaccuracy of +/−0.5 mm or more, which is problematic for subsequent receiver assembly processes. It is therefore desirable to control component positioning accuracy on a DBC substrate during the component attachment process.